1. Field of the Invention
This invention provides a novel function for a conserved domain in the extracellular region of the members of the TNF receptor (TNFR) superfamily in mediating specific ligand-independent assembly of receptor oligomers.
2. Background Art
The members of the TNFR superfamily typically contain one to six cysteine rich domains in their extracellular regions, a single transmembrane domain and variably sized intracytoplasmic domains. The members of this receptor family typically bind to ligands of the TNF cytokine family that are defined by structural, functional and sequence similarities. These receptors form trimers in their active liganded state and several members contain a cytoplasmic domain referred to as a death domain. According to the present invention, the extracellular region of these receptors is further characterized by a novel self-association or homotypic association function that is mediated via a pre-ligand receptor assembly domain (PLAD) that contains at least one cysteine rich domain More specifically, members of the TNFR superfamily, including TRAIL receptor 1,CD40, 60 kDa TNFR and 80 kDa TNFR show this homotypic association. Other members of the TNFR superfamily, including Fas, LTβR, CD40, CD30, CD27, HVEM, RANK, OX40 and DR4 contain this PLAD. The PLAD is necessary for ligand binding and receptor function. Thus, members of the TNFR superfamily appear to signal through distinct pre-formed complexes rather than through ligand-induced cross-linking of individual receptor subunits. Therefore, PLAD can be targeted by pharmaceutical agents in order to block the formation of these preformed complexes and thus block receptor function.